Effects of antibiotics on Pseudomonas aeruginosa NK125502 and Pseudomonas fluorescens MF0 biofilm formation on immobilized fibronectin

The effect of subminimal inhibitory concentration (1/2 MIC) of antibiotics on the biofilm formation on immobilized fibronectin by Pseudomonas was investigated by examining the reference strains NK125502 P. aeruginosa and MF0 P. fluorescens in a microtiter plates assay. When the antibiotics were added during bacterial growth and biofilm development, gentamicin was the only antimicrobial agent tested which decreased significantly the biofilm formation by the two strains. Cefsulodin and chloramphenicol also decreased the P. aeruginosa biofilm development (P<0.01), whereas polymyxin B inhibited biofilm formation by P. fluorescens (p<0.05). When the antibiotics were only present during bacterial growth and not during biofilm development, gentamicin was the only antibiotic tested to decrease significantly the biofilm formation by P. aeruginosa for incubation times of 20 and 72h (P<0.01), whereas P. fluorescens was not affected. This persistent inhibition of P. aeruginosa biofilm formation may be interesting in intermittent antibiotherapy treatments.